Planning Evaluation of C-Arm Cone Beam CT Angiography for Target Delineation in Stereotactic Radiation Surgery of Brain Arteriovenous Malformations

Abstract

Purpose Stereotactic radiation surgery (SRS) is one of the therapeutic modalities currently available to treat cerebral arteriovenous malformations (AVM). Conventionally, magnetic resonance imaging (MRI) and MR angiography (MRA) and digital subtraction angiography (DSA) are used in combination to identify the target volume for SRS treatment. The purpose of this study was to evaluate the use of C-arm cone beam computed tomography (CBCT) in the treatment planning of SRS for cerebral AVMs. Methods and Materials Sixteen consecutive patients treated for brain AVMs at our institution were included in this retrospective study. Prior to treatment, all patients underwent MRA, DSA, and C-arm CBCT. All images were coregistered using the GammaPlan planning system. AVM regions were delineated independently by 2 physicians using either C-arm CBCT or MRA, resulting in 2 volumes: a CBCT volume (VCBCT) and an MRA volume (VMRA). SRS plans were generated based on the delineated regions. Results The average volume of treatment targets delineated using C-arm CBCT and MRA were similar, 6.40 cm3 and 6.98 cm3, respectively (P = .82). However, significant regions of nonoverlap existed. On average, the overlap of the MRA with the C-arm CBCT was only 52.8% of the total volume. In most cases, radiation plans based on VMRA did not provide adequate dose to the region identified on C-arm CBCT; the mean minimum dose to VCBCT was 29.5%, whereas the intended goal was 45% (P<.001). The mean volume of normal brain receiving 12 Gy or more in C-arm CBCT-based plans was not greater than in the MRA-based plans. Conclusions Use of C-arm CBCT images significantly alters the delineated regions of AVMs for SRS planning, compared to that of MRA/MRI images. CT-based planning can be accomplished without increasing the dose to normal brain and may represent a more accurate definition of the nidus, increasing the chances for successful obliteration.

Integration of rotational angiography enables better dose planning in Gamma Knife radiosurgery for brain arteriovenous malformations

“…Conformity is one of the most important dosimetric factors for radiosurgery, 29 with several authors suggesting that conformal radiotherapy significantly reduces radiation-induced adverse events by decreasing the toxicity to healthy tissues 11,16,23 and that dose escalation delivered by conformal radiotherapy may improve the radiosurgical efficacy without increasing the toxicity. 2,3 Although the efficacy of RA for other radiotherapy modalities (e.g., Cy-berKnife) has been studied previously, 9,10,18,36,38 their results should not be applied unthoughtfully to GKS, as the radiosurgical planning process used in those modalities is totally different from that used in GKS. To date, few studies examining the efficacy of RA in GKS have been reported, and no detailed analyses of dosimetric variables like those performed herein have been performed previously.…”

Application of Time-Resolved 3D Digital Subtraction Angiography to Plan Cerebral Arteriovenous Malformation Radiosurgery

“…12 Other small-series studies also used combined imaging, including 3D rotational angiography, for radiosurgery treatment planning. 14,23,24 However, the hemodynamics and temporal information inherent in 3D rotational angiography are limited.…”

Technological quality requirements for stereotactic radiotherapy

“…Volumetric contrast-enhanced thin-slice (max. 1-1.5 mm) MRI and/or high-resolution contrast-enhanced CT scans and/or cone-beam computed tomography (CBCT) angiography are considered alternative imaging modalities [3,10,15], but typically lack detailed hemodynamic information compared to DSA imaging.…”